This invention relates to a communication terminal device for connecting plural channels with a communication network through settable user-network interfaces.
The prior art will be explained assuming that the communication network is an ISDN (integrated services digital network). The INS (information network system) which is ISDN provided by NTT Co. Ltd in accordance with the CCITT recommendation I-series has two user-network interfaces, i.e., a basic rate user-network interface (BRI) and a primary rate user-network interface (PRI). Using the same called party number, two user information transfer channels (B channels) can be set on BRI and 23 B channels can also be set on PRI. An address can be set for each user-network interface. A subaddress can be set on each communication terminal connected with the user-network interface.
In such a communication network, where a called terminal (called communication terminal device) and a calling terminal (calling communication terminal device) are connected using two B channels simultaneously, the called terminal will have the two B channels allotted with the same address. Thus, the calling terminal repeatedly calls one called address and called subaddress input by a user into the network for the two B channels so that the two B channels can be established between the calling terminal and the called terminal. In this way, in the same series of calling procedures as where a user intends to connect one channel, it is possible to direct the communication terminal to connect plural communication channels.
However, there are cases where an address is allotted not for each user-network interface, but each B channel included in each user-network interface. In this case, different addresses are allotted for different B channels. Further, in some countries, the user-network interface including only one B channel is provided. In this case, in order to assure plural B channels, plural user-network interfaces are necessary. In both cases, one communication terminal has plural B channels allotted with different addresses. Thus, it is necessary to give plural channels plural addresses so that the above cases are not dealt with by the repeated calling processing by the calling terminal. It was therefore necessary to repeat the calling procedure for one called party address and subaddress for connection of one channel by the number of times corresponding to the number of channels.